1. Field of the Invention
The preferred embodiments of the present invention are directed to maintaining historical databases of information. More particularly, the preferred embodiments are directed to an in-place dynamically re-sizeable historical database for gas flow measurement and logging systems.
2. Background of the Invention
Since the advent of computer systems, engineers have used the computer to monitor and control real-time systems. Part of the monitoring feature is the ability to maintain databases of historical information regarding the parameters or processes monitored and/or controlled. Without regard to hardware constraints imposed by physical systems, the most logical way to store logged information or data is to write the information to a memory, for example a random access memory (RAM) location, and also write a corresponding time-stamp. In such an oversimplified scheme, the frequency at which data is sampled and written is of no concern. Each parameter may be sampled, written to the historical database, and correspondingly time-stamped without regard to other parameters in the historical database or the physical size of the memory device.
The scheme described where each stored parameter has a corresponding time-stamp, while possible, is not practical in that such a database may require significant electronic storage space. In order to address this problem, the related art approach has been to sample the parameters substantially simultaneously, write the parameter values to the database, and apply a single time-stamp applicable to all the entries. The greater number of parameters that can be associated with a single time-stamp, the greater the space savings in long-term storage. FIG. 1 shows, in a more graphical form, the related art method of having one time-stamp associated with multiple parameters. In particular, FIG. 1 shows that a time-stamp 4A may be associated with multiple parameters 1, 2 and 3. Progressing from the top of the figure to the bottom, each time-stamp 4A–4E represents the time in which the parameters 1, 2 and 3 were recorded in the historical database.
While such an arrangement represents an improvement over having a time-stamp associated with each parameter written, problems still exist. For example, should one of the parameters need to be logged (written to the database) at an unscheduled time, each and every parameter associated with the time-stamp must be written. While the exemplary system of FIG. 1 shows only three parameters 1, 2 and 3 associated with each time-stamp 4A–4E where tens or hundreds of parameters are associated with a single time-stamp, logging each of the parameters simply because only one of the parameters is needed quickly erodes the space savings associated with the time-stamping procedure.
Yet another problem exists with storing data in the fashion described in FIG. 1; namely, there is not a way to modify the number of samples of a parameter or group of parameters associated with the single time-stamp without likewise affecting all the parameters logged.
Thus, what is needed in the art is a structure and method to increase time-stamping efficiently for multiple parameters with the ability, however, to dynamically re-size the historical information.